1. Field of the Invention
The present invention relates generally to a safety device, and particularly to a device for safely raising and lowering a person using the single-rope technique.
2. Technical Background
There are many types of work that require a climbing device to safely perform a given task. In tree care work, for example, pruning, branch cutting and similar tasks must be performed off the ground and in the tree itself. There are construction jobs that also require the user to work in elevated positions. Some users enjoy mountain climbing or rock climbing as a recreational pursuit. Whatever the activity, it is paramount that the persons engaging in activities such as these be able to ascend, work and descend, safely and effectively, without worry or concern.
In reference to FIG. 1, a diagrammatic depiction of the “two-rope technique” is shown. Here, a rope R is disposed over a support structure Sp. One end of the rope is coupled to an attachment point 2-2 of the apparatus 2, is secured by clamp 2-1, and extends toward the ground. The user is attached to the apparatus at the attachment point 2-2. To ascend, the user pulls the rope R downwardly (See arrow A) at point “P” to pull the apparatus 2 upwardly (See arrow B) toward the support structure. At rest, the clamping structure 2-1 secures the user at some position off the ground. When the user wishes to descend, he depresses the release mechanism 2-3; the attachment mechanism works in conjunction with the clamp 2-1 to apply enough friction and control such that the user slides down the rope in safe manner. One drawback to the two-rope technique relates to the 2:1 mechanical advantage provided by the two-rope technique; while it is relatively easy to pull oneself up the rope, one only travels half as far. Some users do not like this technique and prefer the single rope technique instead.
Referring to FIGS. 2A-2B, a diagrammatic depiction of the “single rope technique” is shown. In this case, one end of the rope R is anchored or secured to the ground. The rope R extends over the support structure Sp, and is secured by the clamp 1-1. The attachment point 1-2 connects the user, or the user's harness, to the climbing apparatus 1, but is not connected to the rope. The single rope technique therefore provides no mechanical advantage. There is a 1:1 relationship between the pulling distance and traveling distance because they are one and the same. One of the drawbacks associated with the single rope technique occurs when the user actuates the release mechanism. Briefly stated, once the clamp 1-1 is released, the user has a tendency to rapidly descend down the rope with little control.
Referring to FIG. 2B, the approach commonly employed to overcome the above stated drawback is shown. In order to obviate the above stated drawback, the user wraps the rope around the clamp 1-1 to effect a technique that is appropriately referred to as a “rope wrap” 1-4. In particular, when the user actuates the release 1-3, she is holding the lower portion of the rope R tightly against the clamp portion 1-1 such that the rope wrap 1-4 increases the coefficient of friction as the rope R moves in the direction A over the clamp 1-1. The applied friction slows the user's descent and allows the user to lower herself with greater control.
One drawback associated with the rope wrap technique occurs at the moment the user actuates the release 1-3. There is a momentary drop, or jerk, that occurs when the release takes up some of the slack in the rope or line. This sudden movement is very unsettling to the user. Many users report a sense of panic and feel unsafe when this occurs. Another drawback to this approach occurs when the user descends to a new position to continue work. Once the user is in position, the release mechanism is disengaged and the clamp secures the rope. Next, the user must undo the rope wrap 1-4. However, this step in the process typically causes another sudden drop. Once again, the user momentarily thinks that she is about to fall. Again, this sudden movement is unsettling and annoying.
What is needed, therefore, is an apparatus adapted to the single rope technique that overcomes the drawbacks described above. In particular an apparatus is needed that avoids the sudden drops associated with the rope wrap and the conventional single rope technique apparatus.